Conventionally, a variety of electronic devices including mobile phones and digital cameras use a mechanical switch in general, such as a tact switch or a membrane switch, which serves as the input apparatus for allowing an operator to perform input operations. These days, especially, it is often the case that small terminal devices are equipped with multiple functions, and such terminal devices have housing with keys and buttons constituted of various switches on a surface thereof.
Generally, such a switch is assigned a single operation (or function based on a program or the like). For example, the mobile phone outputs a number corresponding to a key upon detection of a pressing input to a numerical keypad, or displays a menu panel upon detection of the pressing input to a menu key.
However, carrying out a plurality of operations in series with different switches assigned respective operations may result in a substantially troublesome task. Although it may be considered to arrange such that, by using a single switch, a plurality of operations are carried out sequentially whenever an input to the switch is detected, such an input method requires predefinition of an order of the operations. Therefore, it is not capable of immediately carrying out arbitrary operations desired by the operator.
In order to address the above problem, there has been suggested an input apparatus capable of assigning a plurality of operations to a switch in accordance with an input state to the switch (for example, see Patent Document 1).
The input apparatus described in Patent Document 1 can receive inputs of two levels in accordance with the pressure loads applied when the operator performs the input operation.
FIG. 8 is a cross-sectional view illustrating a schematic internal structure of an operation apparatus 100 described in Patent Document 1. As shown in FIG. 8, the operation apparatus 100 has a first detection unit 200 and a second detection unit 300, both of which are constituted of membrane switches. The second detection unit 300 is arranged (in a pressing direction by the operator) under the first detection unit 200. An area to be directly contacted by a finger F of the operator is made of a flexible member. In this way, the plastic member bends under the pressure on the operation apparatus 100 by the operator, thereby conveying the pressure load to the first detection unit 200. On the operation apparatus 100, when the operator presses down a position corresponding to a first contact point S3, applying a light weight (first operation force) with the finger F, a first upper conductive portion 201c and a first lower conductive portion 202c come into contact with each other, allowing for conduction of the first contact point S3. This is defined as a first level input. On the operation apparatus 100, further, when the finger F presses down applying a heavier weight (second operation force), a second upper conductive portion 301c and a second lower conductive portion 302c come into contact with each other, allowing for conduction of a second contact point T3. This is defined as a second level input. FIG. 8 shows a state that the first contact point S3 detects the first level input, and the second contact point T3 also detects the second level input as the operator's finger F presses the operation apparatus 100 applying the second operation force.
Since such an input apparatus receives inputs of two levels in accordance with the pressure loads of the operator's input, different operations can be assigned to respective levels. Such an input apparatus allows the operator to separately perform a plurality of inputs by adjusting the pressure on one switch (input apparatus) in a single input operation, a pressing input to the switch.
That is, such an input apparatus for receiving inputs of two levels enables the operator to perform the first level input by maintaining light pressure on the button. This input state is called “halfway pressing”, and referred to as the “first level input” hereinafter. This input apparatus also enables the operator to perform the second level input by pressing the button with pressure heavier than the first level input. This input state is called “full pressing”, and referred to as the “second level input” hereinafter.
A shutter button of a camera is an example of typical application of the input apparatus as the mechanical switch for receiving inputs of two levels in accordance with the pressure loads. In general, for the mobile phones and the like having a digital camera function, the “halfway pressing” for the first level input by the operator allow to turn on functions for adjusting AE (Auto Exposure) and AF (Auto Focus). If the operator inputs with the “full pressing” for the second level input in this state, the shutter is released. Accordingly, the above mechanical switch can be assigned different operations for the first level input and the second level input, and thus the operator can separately operate the different operations as desired.
It is to be noted that the input apparatus for receiving inputs of a plurality of levels in accordance with the pressure loads is not limited to the mechanical switch. For example, there has been suggested a touch panel type input apparatus, a combination of a display unit and a position input device, for receiving inputs of a plurality of levels in accordance with the pressure loads by software processing (for example, see Patent Document 2).
The touch panel type input apparatus described in Patent Document 2 has a position detection unit for detecting a position of a pressing operation on the touch panel provided on a screen of the display unit, and a pressure detection unit for detecting a pressing force applied on the touch panel. This input apparatus is capable of receiving inputs of two systems, an input in accordance with a position detected by the position detection unit and multi-level inputs in accordance with the pressure detected by the pressure detection unit, in one pressing operation of the touch panel by the operator.
That is, with this input apparatus, the operator can simultaneously perform both an input of a first system in accordance with a position of the pressing operation and an input of a second system in accordance with a pressure on the touch panel at that time, by performing the pressing operation to the touch panel on the screen. At this time, the input apparatus can receive multiple levels of selections, i.e., three or more levels of selections in accordance with the pressure on the touch panel. Accordingly, the operator can perform an input of the two systems at once in a single pressing operation of the touch panel, which enables reduction in the number of pressing operations.
As stated above, both of the input apparatus using the mechanical switch and the input apparatus using the touch panel can receive inputs of a plurality of levels in accordance with the pressure loads. Those input apparatuses allow collection of a plurality of functions to one button or key by classifying inputs into a plurality of levels in accordance with the pressure loads. Thereby, it is possible to reduce the number of keys and buttons for input operations. Especially for small terminals such as the mobile terminals, there is a difficulty in arranging numerous keys and buttons on their bodies due to a small size of their housings. Accordingly, if the mobile terminal can separately perform a plurality of functions with a small number of keys and buttons, it can advantageously reduce the keys and buttons necessary on the terminal body.